1. Field of the Invention
This invention relates in general to electronic devices, and more particularly, to electronic devices comprising gamma correction units, processes for using those electronic devices, and data processing system readable media having code including instructions for carrying out at least a portion of the processes.
2. Description of the Related Art
Organic electronic devices have attracted considerable attention since the early 1990's. Examples of organic electronic devices include Organic Light-Emitting Diodes (“OLEDs”), which include Polymer Light-Emitting Diodes (“PLEDs”) and Small Molecule Organic Light-Emitting Diodes (“SMOLEDs”). Display devices, including OLED displays, have played an important role in modern human life. As computing, telecommunications, home entertainment, and networking technologies converge, the display unit will become more important.
In the display area, there are many kinds of technologies including cathode ray tube (“CRT”), liquid crystal display (“LCD”), and so on. LCD technology is dominant in the present flat panel display market. FIG. 1 includes a block diagram of a conventional data driver 100 for use with an LCD display.
FIG. 1 includes a block diagram of the conventional data driver 100. R, G, and B data, from external digital video inputs for Red, Green and Blue electronic components, are received by a data control unit 102 and are routed to a data latch unit 122. An address shift register 104 receives an external enable signal, a shift direction signal, and a shift clock signal. The external enable signal is used to enable the address shift register 104. The shift direction signal controls the shift direction (from scan line 1 to scan line n or from scan line n to scan line 1). The shift clock signal provides a reference timing signal from which activities in the conventional data driver 100 can be coordinated. The data latch unit 122 also receives a latch enable signal and a load signal. The data latch unit 122 may or may not include storage registers. If storage registers are present, data can be transferred from individual data latches to their corresponding storage registers. The latch enable signal is used to enable individual data latches (or storage registers, if present) within the data latch unit 122, and the load signal enables the captured datum for each data latch to be output to digital-to-analog (“D/A”) converters 124. The D/A converters 124 also receive a signal from a gamma correction unit 142 and a polarity inverter 144. Outputs from the D/A converters 124 are received by output-signal drivers 126, which can send data along data lines to electronic components within an array of a display. The operation of the data driver 100 is conventional.
Regarding the gamma correction unit 142, displays and printers use a gamma function to better match the intensity of the output to what a user would expect to see or desires. For example, for an image, a gamma correction unit can provide a gamma function that allows the image, as seen by a human on a display or on paper, to match the intensity if the human were present when the image was actually captured (e.g., when the picture was taken). Gamma correction using a gamma function is conventional. The gamma correction unit receives an input signal corresponding to an image and produces an output signal (Vo) based in part on the value of gamma as given in Equation 1.Output signal=(Input signal)γ  (Equation 1)
FIG. 2 illustrates a series of lines (straight and curved) for different values of gamma. As can be seen in FIG. 2, a gamma of less than 1 is used for lighter images, and a gamma of greater than 1 is used for darker images.
The value of gamma for the gamma correction unit 142 is set when the gamma correction unit is fabricated and cannot be changed at a later time. Also, the minimum and maximum output values from the gamma correction unit are set when the display or printer is fabricated and are not changed at a later time. Therefore, the gamma function is static.
For organic electroluminescent displays, multiple gamma correction units have been proposed. For example, one gamma correction unit may be dedicated to each color emitter (e.g., red, green, and blue). However, the gamma function is still static and does not change. The problems with the gamma correction unit 142 may be even more of an issue for organic active layers used within radiation-emitting components, as different materials for organic active layers and corresponding thin-film pixel driving circuits may degrade at different rates.